text: //===---- CGLoopInfo.h - LLVM CodeGen for loop metadata -*- C++ -*---------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This is the internal state used for llvm translation for loop statement
  // metadata.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CLANG_LIB_CODEGEN_CGLOOPINFO_H
  #define LLVM_CLANG_LIB_CODEGEN_CGLOOPINFO_H
  
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/IR/DebugLoc.h"
  #include "llvm/IR/Value.h"
  #include "llvm/Support/Compiler.h"
  
  namespace llvm {
  class BasicBlock;
  class Instruction;
  class MDNode;
  } // end namespace llvm
  
  namespace clang {
  class Attr;
  class ASTContext;
  namespace CodeGen {
  
  /// Attributes that may be specified on loops.
  struct LoopAttributes {
    explicit LoopAttributes(bool IsParallel = false);
    void clear();
  
    /// Generate llvm.loop.parallel metadata for loads and stores.
    bool IsParallel;
  
    /// State of loop vectorization or unrolling.
    enum LVEnableState { Unspecified, Enable, Disable, Full };
  
    /// Value for llvm.loop.vectorize.enable metadata.
    LVEnableState VectorizeEnable;
  
    /// Value for llvm.loop.unroll.* metadata (enable, disable, or full).
    LVEnableState UnrollEnable;
  
    /// Value for llvm.loop.unroll_and_jam.* metadata (enable, disable, or full).
    LVEnableState UnrollAndJamEnable;
  
    /// Value for llvm.loop.vectorize.width metadata.
    unsigned VectorizeWidth;
  
    /// Value for llvm.loop.interleave.count metadata.
    unsigned InterleaveCount;
  
    /// llvm.unroll.
    unsigned UnrollCount;
  
    /// llvm.unroll.
    unsigned UnrollAndJamCount;
  
    /// Value for llvm.loop.distribute.enable metadata.
    LVEnableState DistributeEnable;
  
    /// Value for llvm.loop.pipeline.disable metadata.
    bool PipelineDisabled;
  
    /// Value for llvm.loop.pipeline.iicount metadata.
    unsigned PipelineInitiationInterval;
  };
  
  /// Information used when generating a structured loop.
  class LoopInfo {
  public:
    /// Construct a new LoopInfo for the loop with entry Header.
    LoopInfo(llvm::BasicBlock *Header, const LoopAttributes &Attrs,
             const llvm::DebugLoc &StartLoc, const llvm::DebugLoc &EndLoc,
             LoopInfo *Parent);
  
    /// Get the loop id metadata for this loop.
    llvm::MDNode *getLoopID() const { return TempLoopID.get(); }
  
    /// Get the header block of this loop.
    llvm::BasicBlock *getHeader() const { return Header; }
  
    /// Get the set of attributes active for this loop.
    const LoopAttributes &getAttributes() const { return Attrs; }
  
    /// Return this loop's access group or nullptr if it does not have one.
    llvm::MDNode *getAccessGroup() const { return AccGroup; }
  
    /// Create the loop's metadata. Must be called after its nested loops have
    /// been processed.
    void finish();
  
  private:
    /// Loop ID metadata.
    llvm::TempMDTuple TempLoopID;
    /// Header block of this loop.
    llvm::BasicBlock *Header;
    /// The attributes for this loop.
    LoopAttributes Attrs;
    /// The access group for memory accesses parallel to this loop.
    llvm::MDNode *AccGroup = nullptr;
    /// Start location of this loop.
    llvm::DebugLoc StartLoc;
    /// End location of this loop.
    llvm::DebugLoc EndLoc;
    /// The next outer loop, or nullptr if this is the outermost loop.
    LoopInfo *Parent;
    /// If this loop has unroll-and-jam metadata, this can be set by the inner
    /// loop's LoopInfo to set the llvm.loop.unroll_and_jam.followup_inner
    /// metadata.
    llvm::MDNode *UnrollAndJamInnerFollowup = nullptr;
  
    /// Create a LoopID without any transformations.
    llvm::MDNode *
    createLoopPropertiesMetadata(llvm::ArrayRef<llvm::Metadata *> LoopProperties);
  
    /// Create a LoopID for transformations.
    ///
    /// The methods call each other in case multiple transformations are applied
    /// to a loop. The transformation first to be applied will use LoopID of the
    /// next transformation in its followup attribute.
    ///
    /// @param Attrs             The loop's transformations.
    /// @param LoopProperties    Non-transformation properties such as debug
    ///                          location, parallel accesses and disabled
    ///                          transformations. These are added to the returned
    ///                          LoopID.
    /// @param HasUserTransforms [out] Set to true if the returned MDNode encodes
    ///                          at least one transformation.
    ///
    /// @return A LoopID (metadata node) that can be used for the llvm.loop
    ///         annotation or followup-attribute.
    /// @{
    llvm::MDNode *
    createPipeliningMetadata(const LoopAttributes &Attrs,
                             llvm::ArrayRef<llvm::Metadata *> LoopProperties,
                             bool &HasUserTransforms);
    llvm::MDNode *
    createPartialUnrollMetadata(const LoopAttributes &Attrs,
                                llvm::ArrayRef<llvm::Metadata *> LoopProperties,
                                bool &HasUserTransforms);
    llvm::MDNode *
    createUnrollAndJamMetadata(const LoopAttributes &Attrs,
                               llvm::ArrayRef<llvm::Metadata *> LoopProperties,
                               bool &HasUserTransforms);
    llvm::MDNode *
    createLoopVectorizeMetadata(const LoopAttributes &Attrs,
                                llvm::ArrayRef<llvm::Metadata *> LoopProperties,
                                bool &HasUserTransforms);
    llvm::MDNode *
    createLoopDistributeMetadata(const LoopAttributes &Attrs,
                                 llvm::ArrayRef<llvm::Metadata *> LoopProperties,
                                 bool &HasUserTransforms);
    llvm::MDNode *
    createFullUnrollMetadata(const LoopAttributes &Attrs,
                             llvm::ArrayRef<llvm::Metadata *> LoopProperties,
                             bool &HasUserTransforms);
    /// @}
  
    /// Create a LoopID for this loop, including transformation-unspecific
    /// metadata such as debug location.
    ///
    /// @param Attrs             This loop's attributes and transformations.
    /// @param LoopProperties    Additional non-transformation properties to add
    ///                          to the LoopID, such as transformation-specific
    ///                          metadata that are not covered by @p Attrs.
    /// @param HasUserTransforms [out] Set to true if the returned MDNode encodes
    ///                          at least one transformation.
    ///
    /// @return A LoopID (metadata node) that can be used for the llvm.loop
    ///         annotation.
    llvm::MDNode *createMetadata(const LoopAttributes &Attrs,
                                 llvm::ArrayRef<llvm::Metadata *> LoopProperties,
                                 bool &HasUserTransforms);
  };
  
  /// A stack of loop information corresponding to loop nesting levels.
  /// This stack can be used to prepare attributes which are applied when a loop
  /// is emitted.
  class LoopInfoStack {
    LoopInfoStack(const LoopInfoStack &) = delete;
    void operator=(const LoopInfoStack &) = delete;
  
  public:
    LoopInfoStack() {}
  
    /// Begin a new structured loop. The set of staged attributes will be
    /// applied to the loop and then cleared.
    void push(llvm::BasicBlock *Header, const llvm::DebugLoc &StartLoc,
              const llvm::DebugLoc &EndLoc);
  
    /// Begin a new structured loop. Stage attributes from the Attrs list.
    /// The staged attributes are applied to the loop and then cleared.
    void push(llvm::BasicBlock *Header, clang::ASTContext &Ctx,
              llvm::ArrayRef<const Attr *> Attrs, const llvm::DebugLoc &StartLoc,
              const llvm::DebugLoc &EndLoc);
  
    /// End the current loop.
    void pop();
  
    /// Return the top loop id metadata.
    llvm::MDNode *getCurLoopID() const { return getInfo().getLoopID(); }
  
    /// Return true if the top loop is parallel.
    bool getCurLoopParallel() const {
      return hasInfo() ? getInfo().getAttributes().IsParallel : false;
    }
  
    /// Function called by the CodeGenFunction when an instruction is
    /// created.
    void InsertHelper(llvm::Instruction *I) const;
  
    /// Set the next pushed loop as parallel.
    void setParallel(bool Enable = true) { StagedAttrs.IsParallel = Enable; }
  
    /// Set the next pushed loop 'vectorize.enable'
    void setVectorizeEnable(bool Enable = true) {
      StagedAttrs.VectorizeEnable =
          Enable ? LoopAttributes::Enable : LoopAttributes::Disable;
    }
  
    /// Set the next pushed loop as a distribution candidate.
    void setDistributeState(bool Enable = true) {
      StagedAttrs.DistributeEnable =
          Enable ? LoopAttributes::Enable : LoopAttributes::Disable;
    }
  
    /// Set the next pushed loop unroll state.
    void setUnrollState(const LoopAttributes::LVEnableState &State) {
      StagedAttrs.UnrollEnable = State;
    }
  
    /// Set the next pushed loop unroll_and_jam state.
    void setUnrollAndJamState(const LoopAttributes::LVEnableState &State) {
      StagedAttrs.UnrollAndJamEnable = State;
    }
  
    /// Set the vectorize width for the next loop pushed.
    void setVectorizeWidth(unsigned W) { StagedAttrs.VectorizeWidth = W; }
  
    /// Set the interleave count for the next loop pushed.
    void setInterleaveCount(unsigned C) { StagedAttrs.InterleaveCount = C; }
  
    /// Set the unroll count for the next loop pushed.
    void setUnrollCount(unsigned C) { StagedAttrs.UnrollCount = C; }
  
    /// \brief Set the unroll count for the next loop pushed.
    void setUnrollAndJamCount(unsigned C) { StagedAttrs.UnrollAndJamCount = C; }
  
    /// Set the pipeline disabled state.
    void setPipelineDisabled(bool S) { StagedAttrs.PipelineDisabled = S; }
  
    /// Set the pipeline initiation interval.
    void setPipelineInitiationInterval(unsigned C) {
      StagedAttrs.PipelineInitiationInterval = C;
    }
  
  private:
    /// Returns true if there is LoopInfo on the stack.
    bool hasInfo() const { return !Active.empty(); }
    /// Return the LoopInfo for the current loop. HasInfo should be called
    /// first to ensure LoopInfo is present.
    const LoopInfo &getInfo() const { return Active.back(); }
    /// The set of attributes that will be applied to the next pushed loop.
    LoopAttributes StagedAttrs;
    /// Stack of active loops.
    llvm::SmallVector<LoopInfo, 4> Active;
  };
  
  } // end namespace CodeGen
  } // end namespace clang
  
  #endif
  